1. Forced Vibration and Resonance

2. Natural Frequencies Nearly all objects, when disturbed, will vibrate. Nearly all objects, when disturbed, will vibrate.

3. Natural Frequencies Objects tend to vibrate at their own particular frequency Objects tend to vibrate at their own particular frequency

4. Natural Frequencies This frequency is known as the natural frequency of the object. This frequency is known as the natural frequency of the object.

5. The glass “harp” http://www.huffingtonp ost.co.uk/2013/02/15/h allelujah-wine-glasses- video_n_2693037.html http://www.huffingtonp ost.co.uk/2013/02/15/h allelujah-wine-glasses- video_n_2693037.html http://www.huffingtonp ost.co.uk/2013/02/15/h allelujah-wine-glasses- video_n_2693037.html http://www.huffingtonp ost.co.uk/2013/02/15/h allelujah-wine-glasses- video_n_2693037.html http://www.youtube.co m/watch?v=S5K- 43bjRwU http://www.youtube.co m/watch?v=S5K- 43bjRwU http://www.youtube.co m/watch?v=S5K- 43bjRwU http://www.youtube.co m/watch?v=S5K- 43bjRwU

6. Resonance

7. Resonance Definition: when the frequency of a vibration on an object matches the object’s natural frequency…a dramatic increase in height occurs Definition: when the frequency of a vibration on an object matches the object’s natural frequency…a dramatic increase in height occurs

8. Resonance An object that is forced at its natural frequency will resonate (vibrate) at that frequency (with increasing amplitude if the forcing continues). An object that is forced at its natural frequency will resonate (vibrate) at that frequency (with increasing amplitude if the forcing continues). Consider the forced vibration of a child on a swing – pushing at the natural frequency increases the amplitude. Consider the forced vibration of a child on a swing – pushing at the natural frequency increases the amplitude.

9. Resonance An object that is forced at its natural frequency will resonate (vibrate) at that frequency (with increasing amplitude if the forcing continues). An object that is forced at its natural frequency will resonate (vibrate) at that frequency (with increasing amplitude if the forcing continues). http://www.youtube.com/watch?v=nHSGd2X1nc8&feature=related http://www.youtube.com/watch?v=nHSGd2X1nc8&feature=related

10. Resonance An object that is forced at its natural frequency will resonate (vibrate) at that frequency (with increasing amplitude if the forcing continues). An object that is forced at its natural frequency will resonate (vibrate) at that frequency (with increasing amplitude if the forcing continues). The Tacoma-Narrows Bridge: The Tacoma-Narrows Bridge: http://www.youtube.com/watch?v=xox9BVSu7Ok

11. Resonance In 1831 soldiers were ordered to “break step” across bridges to avoid producing a frequency equal to the natural frequency of the bridge. In 1831 soldiers were ordered to “break step” across bridges to avoid producing a frequency equal to the natural frequency of the bridge. According to accounts of the time, the bridge broke apart beneath the soldiers, throwing dozens of men into the water. According to accounts of the time, the bridge broke apart beneath the soldiers, throwing dozens of men into the water.

12. Resonance: Example For example, the sound wave produced by a vibrating tuning fork will cause an identical tuning fork to start vibrating. For example, the sound wave produced by a vibrating tuning fork will cause an identical tuning fork to start vibrating.

13. Examples of resonance 1) breaking glass 1) breaking glass 2) bridges 2) bridges 3) walls (walls of Jericho) 3) walls (walls of Jericho) 4) radio stations 4) radio stations 5) microwave ovens…water molecules in food vibrate and resonate and heat up 5) microwave ovens…water molecules in food vibrate and resonate and heat up